Charged particle beam switching apparatus



1966 .HERRERA 3, 87,583

CHARGED I BEAM SWITCHING APPARATUS 1 ed Jan. 28, 1964 p/e/oxz ART I Y J 4? 15 44 United States Patent 3,287,583 CHARGED PARTICLE BEAM SWITCHING APPARATUS John C. Herrera, Stoneham, Mass., assignor to High Voltage Engineering Corporation, Burlington, Mass., a corporation of Massachusetts Filed Jan. 28, 1964, Ser. No. 340,704 1 Claim. (Cl. 313-75) This invention relates to the utilization of high energy charged particle beams such as are generated by linear accelerators, Van de Graaif generators and the like. More particularly, it comprehends improved beam switching apparatus adapted to meeting the requirements of high energy, high intensity charged particle beams. The mechanical problems involved in establishing a vacuum chamber between the very large magnet pole pieces of such a high energy beam switching device are solved by the removable flanged vacuum chamber of the present invention.

It is a principal object of this invention to provide new and improved beam switching apparatus for use in conjunction with high energy charged particle beams.

It is another object of this invention to provide beam switching apparatus for use in conjunction with high energy charged particles beams having a removable vacuum chamber whereby the switching apparatus can be conveniently assembled and disassembled.

It is still another object of the invention to provide, in switching apparatus of the type described, a removable vacuum chamber adapted to be positioned between the pole piece faces thereof without requiring an appreciable increase in the gap space therebetween.

These, togther with other objects and features of the invention will become more readily apparent from the fol lowing detailed description taken in conjunction with the accompanying drawings wherein like elements are given like reference numerals throughout and in which:

FIGURES 1 and 2 illustrate in elevation and plan views respectively a particle accelerator and beam switching magnet arrangement of the type to which the present invention can be applied;

FIGURE 3 is a sectional view of the prior art beam switching magnet of FIGURE 2 taken at 33;

FIGURE 4 is a sectional view of the beam switching magnet of FIGURE 3 taken at 4-4;

FIGURE 5 is a plan view of the novel vacuum chamber comprehended by this invention; and

FIGURE 6 is a sectional view of a beam switching magnet as modified in accordance with the principles of the invention illustrating the relationship of the novel vacuum chamber therewith.

Referring now to FIGURES 1 and 2, particle accelerator 7 generates a charged particle beam that is directed to beam switching magnet 8 through evacuated conduit 10. The charged particle beam may then be switched by switching magnet 8 to any of a plurality of targets 9 through evacuated conduits 24 through 28. In such an arrangement the charged particle beam is maintained in vacuum until it is utilized at the target. This, of course, means that a vacuum must be established between magnet pole faces 15. FIGURES 3 and 4 illustrate a prior art arrangement adapted to accomplish this. The switching magnet 8 of FIGURE 3 comprises magnet pole pieces 30, 31 and magnet coils 11. The magnet coils are wound within recessed portions 14 of the magnet pole pieces as shown. Notches 29 are milled from the edges of pole piece faces 15 to accommodate vacuum chamber wall member 13. A vacuum chamber 12 is thus established which utilizes pole faces 15 as the two large area boundaries. Evacuated conduits and 24-28 are coupled to vacuum chamber '12 through vacuum chamber wall member 13 by conventional vacuum sealing techniques. The

3,287,583 Patented Nov. 22, 1966 ice trajectories 1-6 by passing an electric current through magnet coils 11. If no current is'passed through the coils, the beam is not deflected and continues on its course through conduit 26. Ha large current is passed through the'coils in one direction, the beam is deflected to conduit 24. A large current passed through the coils in the opposite direction deflects the beam in the opposite direction to conduit 28. An intermediate current through the coils provides intermediate deflection to conduits 25 and 27.

Although switching magnets of this type have in the past proved satisfactory, the design principles thereof for various reasons are not compatible with the requirements of the larger devices currently being produced to switch very high energy beams. For example, with a relatively small switching magnet, it is acceptable that the pole pieces be permanently joined through wall member 13. Such a switching magnet would not be prohibitively unwieldy. However, switching magnets of the type comprehended by this invention often require massive pole pieces which make a demountable assembly particularly desirable. Furthermore, the pole face areas of these switching magnets are very large and making a satisfactory vacuum tight seal between the wall member and the notched pole face edges becomes extremely difiicult.

The present invention comprehends a separate, removable vacuum chamber which can be inserted between the pole piece faces of a large beam switching magnet as a means for overcoming these difiiculties. In addition to the concept of a separate removable vacuum chamber other features of the invention, hereinafter described, are required to effect an operable device.

The physical and electrical characteristics associated with beam switching magnets of the type comprehended herein greatly influence the design of such a vacuum chamber. Of primary concern is the space between the pole piece faces. The distance between the pole piece faces must be kept to a minimum in order to keep the power requirements of the magnet coils within reasonable limits. Also, because of the extended area of the pole piece faces of a large beam switching magnet, the mechanical strength of a removable vacuum chamber becomes a problem. That is, if the vacuum chamber walls are thin to be consistent with the requirement of minimum gap space between pole piece faces, then the pressure created by the vacuum within may cause the whole chamber to collapse.

Having reference now to FIGURES 5 and 6, there is illustrated thereby apparatus embodying the principles of this invention including a switching magnet having pole piece faces in minimum spaced relationship and a removable vacuum chamber of adequate mechanical strength. The vacuum chamber 17 of FIGURE 5 is fabricated of a sheet metal such as copper and has at least one arcuate flange 18 disposed on both its top and bottom surfaces. It can be readily seen that flanges 18 provide the necessary reinforcement to mechanically strengthen the vacuum chamber. It is important that the proper arc radius be selected for any given application in order that the deflection properties of the magnet pole pieces be substantially unaffected. For each flange 18 that is provided on the surface of vacuum chamber 17, there must also be a groove 21 of similar configuration provided in the adjacent pole piece face. The flanges and grooves are fabricated such that they mate with each other in the manner indicated in FIGURE 6. With this arrangement the reinforcing flanges 18 are employed without the necessity of increasing the distance between pole piece faces. Referring again to the matter of selecting the proper arc radius for flanges 1-8 and grooves 21, it is pointed out that the arc: radius should be such that the charged particle beam skilled in the art. invention be limited to the specific arrangement shown and described and it is intended to cover in the appended J is substantially perpendicular to the arc tangent for any ng o b a fle t on- I o erm ords, if he g ve.

21 in the magnet pole pieceface is at right angles to the course of the beam, it will have virtually no effect on the deflecting properties of the magnet. .It is, of course, recognized that should a deflecting influence resulting from such a groove be desired, then a groove oriented to effect such deflecting influence could be employed. The

space centrally located on the pole piece faces beyond the point where the beam is deflected by the magnet also has gized and the magnetic field deflects the beam before it reaches the space. An additional flange 19 may therefore be provided'in this area should greater reinforcement of the vacuum chamber be required.

While it has been shown and described what is considered at present to be a preferred embodiment of the invention, modifications thereto will readily occur to those It is not therefore desired that the claims all such modifications that fall within the true spirit and scope of the invention.

What is claimed is:

Charge particle beam switching apparatus including first and second magnet means in close parallel relationship adapted to deflect a charged particle beam passing therethrough to any of a plurality of courses of travel, each of said magnet means having at least one arcuate groove therein, said arcuate groove being disposed on the inner adjacent surfaces of said magnet means and positioned such that said charged particle beam will be normal thereto at each of said courses of travel, and a metal vacuum chamber disposed between said magnet means, said vacuum chamber being adapted to contain said charged particle beam and having outwardly protruding arcuate flanges on the surfaces thereof proximate to said magnet means, said flanges being co-extensive with said arcuate grooves and mating therewith.

No references cited.

JAMES W. LAWRENCE, Primary Examiner.

R. SEGAL, Assistant Examiner. 

